The invention relates to a rotary tool effective as a drilling and chamfering tool for drilling and chamfering in one common drill advancing movement, having a tool holder comprising a base body having a longitudinal axis and oppositely located ends. A drill is concentrically clamped in the base body relative to the longitudinal axis to project from one of the ends of the base body. A chamfering tool is located at the one end of the base body and includes a chamfer cutter having a tip displaceable toward the drill and into a region of a lateral free face of the drill.
Such a tool, known from DE-U-92 06 148 has a carriage on the end toward the drill of the base body clamping the drill shank, which is equipped with a cutter body for chamfering and can be displaced in respect to a lateral free face of the drill, as the support of a cutter body, which countersinks or chamfers the drill hole drilled by the drill during the advancing movement taking place in the axial direction of the drill. By means of this it is possible to produce such drilling and chamfering tools of any arbitrary drilling diameter, using standard drills. The chamfering tool or the chamfering cutter, which is to be combined with the drill, can be flexibly adapted to the working diameter of the drill because of the carriage-like advancement ability. In the process, drills with the same shank diameter can be clamped into one base body, however, the working diameter of the individual drill to be clamped into the same base body can deviate from the uniform shank diameter.
If in such a drilling and chamfering tool a standard drill with a working diameter A is replaced by a standard drill with another working diameter B, the chamfering tool must be adapted to the operating diameter of the new drill. This is accomplished by means of a carriage-like adjustability in respect to the base body. In the known tool of the type mentioned at the outset, this adjustment or advancing direction of the chamfering tool forms an acute angle with the drill axis. This means that the standard setting is changed by the advancing movement of the chamfering tool. This standard setting is the distance of the cutting tip of the chamfering tool from the drill tip. Thus, a change of the working diameter of the drill inevitably means a change of the standard setting. A new setting of the drill depth is therefore always required to keep the chamfering depth of the tool constant, following a change of diameter.